The magnetostatic wave device comprises a single crystal substrate made of Gd 3 Ga 5 O 12 , a magnetic garnet single crystal film provided on the single crystal substrate and at least one transducer provided on the magnetic garnet single crystal film. The magnetic garnet single crystal film has {111} plane and is made of a material expressed by the formula (YR 1 ) 3 (FeR 2 ) 5 O 12 , where R 1 is at least one element selected from La, Bi, Lu and Gd, R 2 is at least one element selected from Ga, Al, In and Sc and Y and Fe are the main components with respect to R 1 and R 2 . In the magnetostatic wave device, a DC magnetic field is applied to the magnetic garnet single crystal film so that a magnetostatic surface wave propagates on the magnetic garnet single crystal film in a direction of 〈110〉 axis on {111} plane of the magnetic garnet single crystal film.